1. Field of the Invention
A new gasoline engine with clean combustion chamber surfaces requires a certain minimum octane fuel in order to operate satisfactorily without pinging or knocking. As hours of operation are accumulated on ordinary fuel compositions, this minimum octane increases in conjunction with the accumulation of combustion chamber deposits, until finally, an equilibrium state is achieved at a minimum octane requirement as high as 6-8 or more octane numbers greater than that for the new engine with clean combustion chamber surfaces. This increase in minimum octane requirement is known as octane requirement increase (ORI). The ORI problem is compounded by certain intake system deposit control additives used in unleaded gasolines, wherein the ORI can be larger and more rapid than even the unleaded base fuel alone.
2. DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 4,160,648 describes an intake system deposit control additive for fuels which is a hydrocarbyl poly(oxyalkylene) aminocarbamate and which, when used in amounts of 30-2,000 ppm in gasoline fuels, does not itself appreciably contribute to ORI or combustion chamber deposits.